Within recent years, hypodermic apparatus has become widely available in the form of disposable devices or units, consisting in may instances of a syringe in association with a hypodermic needle. The hypodermic needle component of such a unit typically includes the usual hollow needle per se, together with connecting means such as a hub or the like, which enables fluid-tight connection of the needle to the syringe outlet. The entire syringe and needle unit and a cap covering the discharge end of the needle may be sealed as an "assembly" into a package or envelope which is opened at the time the hypodermic syringe and needle unit is to be used, at which time the unit is removed in a relatively sterile condition.
In common devices of the foregoing type, the syringe and needle unit often includes a relatively small, simple cylindrical cover, the open end of which frictionally engages with and is held by the hub portion of the unit. This cover is removed prior to use of the hypodermic apparatus, after which the device is filled in the usual manner by the medical practitioner, and then utilized to effect the required injection. In general, it is then contemplated that the used needle and syringe unit will be discarded, i.e. the unit, as mentioned, is deemed disposable.
In disposable devices of the aforementioned type, it has unfortunately been repeatedly found that, upon completion of the patient injection, the then uncovered hypodermic device, rather than being immediately discarded, is often placed on a table or other convenient surface. In such condition the uncovered device constitutes a serious hazard, i.e. it may continue to lie in such a position that an individual may inadvertently be injured by the exposed needle. In the event the used needle makes contact in this manner with a patient or medical attendant, not only is the danger of injury high, but moreover, since the needle has been utilized in injection of a patient, it may readily be contaminated with organisms which can effect disease transfer to the individual making contact with same. A specific danger, of course, is the well recognized possibility for thus transmitting serious diseases.
While it might be thought a simple matter to avoid these hazards by simply replacing the needle in its cover, the cover in fact is very difficult to replace because of the need to accurately guide the needle into the narrow opening defined at the mouth of the cover. Specifically the user must hold the small cylindrical cover with one hand, while accurately aiming the needle top and advancing same into the said opening. Indeed, it is all too easy for the practitioner to puncture his or her finger with the needle while trying to guide the needle back into the small cover. In one study, it was thus reported that 50% or more of needle injuries occur while recapping or disposing of needles. See R. McCormick et al. "Epidemiology of Needle Stick Injuries in Hospital Personnel". Amer. J. Med.. V. 70, April, 1981.
From time to time, proposals have been made for constructing disposable hypodermic devices of the aforementioned type as a needle assembly including a covering element which is permanent in nature but retractable. The objective of a construction of this type is partially one of assuring that the cover remains with the needle, so that there may be increased assurance that the cover will be replaced subsequent to use of the device. An example of this type of device may be seen, for example, in U.S. Pat. No. 3,134,380. An improved construction is shown in my prior U.S. Pat. No. 4,139,009. While, therefore, the advantages of a retractable cover construction have been appreciated in the prior art, the relative complexity of prior constructions has been a deterrent to their widespread use. In some cases, comparatively high cost has also been a disadvantage. Furthermore, prior devices do not prevent reuse of hypodermic needles should they be found, e.g. by drug addicts, after they have been used, with the attendant danger of the spread of disease. There is a need, therefore, for a simpler and less expensive covering for a hypodermic needle which, however, can be safely and easily employed, as well as for a covering which will preclude reuse of the needle.